Hip arthroscopy traction weight key to nerve outcome

By Lynda Williams, Senior medwireNews Reporter

Minimizing traction weight during hip arthroscopy in the lateral position may protect against sciatic nerve injury, report US surgeons.

The average maximum traction weight for patients with and without nerve dysfunction or injury was 38.1 and 32.9 kg, respectively, so that the risk for an adverse nerve event increased by 4% for each 0.45 kg increase in traction, after adjusting for age and gender, report Jessica Telleria (University of Washington, Seattle) and co-authors.

However, intraoperative findings from the 60 patients with transcranial motor (tcMEP) and/or somatosensory (SSEP) evoked potential recordings during surgery did not demonstrate a discrete threshold for traction weight or duration that increased the risk for nerve injury or dysfunction.

"Therefore, the surgeon should seek to identify situations in which the traction can be reduced or released to decrease tension on the sciatic nerve," the team recommends, such as removing negative pressure/suction seal from the hip before traction and increasing traction slowly while monitoring with a fluoroscope.

Overall, 58% of patients had nerve dysfunction - defined as a 50% reduction in tcMEP or SSEP amplitude or a 10% decrease in SSEP latency - and 7% of patients sustained a clinical nerve injury causing sensory or motor deficit.

Telleria et al note that all four patients with clinical nerve damage showed tcMEP or SSEP changes and 35 patients showed subclinical effects, whereas there were no such changes in the 25 patients without any nerve events.

"The findings of this study suggest that SSEP/tcMEP evidence of nerve dysfunction can serve as a clinically useful early-warning system for impending nerve injury," they suggest in the Journal of Bone and Joint Surgery.

Contrary to their hypothesis and previous findings, there was no significant difference in total traction time between patients with and without nerve events, at 95.9 and 82.3 minutes, respectively.

However, the researchers admit that their study did not monitor the impact of traction weight or duration on the pudendal nerve and they are unable to rule traction time out as a potential concern.

In an accompanying commentary, Patrick Birmingham (NorthShore University Health System, Chicago, Illinois, USA), says that it would be "logical" for excessive traction time to cause compression or ischemia injuries and that this is more likely to affect the pudendal nerve rather than sciatic nerve.

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